Data and code from: Application of infrared thermography coupled with Eulerian Video Magnification to monitor vital signs in wild seals, from sandy beaches to icy shores

Metabolic rate is a critical indicator of animal health, with respiration
and heart rate used as common proxies for energetic expenditure. Infrared
thermography (IRT) was previously paired with Eulerian video magnification
(EVM) to capture changes in temperature associated with exhalation and
blood flow for accurate and non-invasive measurements of respiration and
heart rate. These techniques have been tested in a range of taxa, but only
in controlled settings at zoological institutions and with imaging
conducted at short range (1 m distance). This study aims to validate
IRT-EVM in wild populations with minimal disturbance and under variable
environmental conditions, and to determine the maximum distance that
animals can be imaged for accurate vital sign measurements. Infrared
videos were taken of pinnipeds in two dramatically different environments,
including northern elephant seals (Mirounga angustirostris, n = 12) in
North America and Weddell seals (Leptonychotes weddellii, n = 23) in
Antarctica. ‘True’ respiration and heart rates were collected
simultaneously by visually monitoring movement of the ribcage/nostrils and
stethoscope/ECG readings, respectively. Using IRT-EVM, respiration rate
was extracted from 74.3 % of individuals while heart rate was measured in
93.3 % of individuals, both with high accuracy (mean absolute error,
respiration rate: 1.3 br~pm; heart rate: 7.4 bpm). Infrared-derived
measurements were resilient to individual characteristics (species, body
mass, molt status, blubber thickness, age class) but were impacted by wind
speed, animal movement, and ambient temperature. Signal noise introduced
by wind could be filtered out to still yield accurate vital signs. Camera
resolution directly influenced the distance that respiration and heart
rates could be measured. In this study, we demonstrate that IRT-EVM is a
powerful, non-invasive method for assessing vital signs in free-living
pinnipeds. These imaging techniques are likely to be applicable towards
study of other mammalian species, with appropriate validations for use in
new field environments to ensure accuracy of IRT-EVM derived vital sign
measurements is maintained. This work makes strides towards monitoring
wildlife metabolic indices to evaluate impacts of intra-annual and
longer-term environmental change on population health.